There are numerous forms of prior art pin locks for securing an insert, with a central mounting hole, within a pocket in a cutting tool. For example, Boyer, U.S. Pat. No. 3,343,431 discloses a tool holder for an insert that employs a cam or eccentric to secure the insert in the holder in the cutting position and to release it therefrom. The holder has a pocket defined by a bottom surface, a side wall, and a back wall that intersects the side wall. A pin is mounted for rotation in a hole in the bottom surface of the pocket. A cam or eccentric is attached to the pin and extends into the pocket for engaging the mounting hole of the insert. The throw of the cam, the distance from the hole in the bottom surface to the walls, and the clearance between the cam, the pin and the holes in which they are located are arranged so that the insert is moved into engagement with the side wall as the pin is rotated from an initial position until the throw of the cam is normal to the side wall. Continued rotation of the pin, in the same rotational direction, forces the insert into engagement with the backwall, while it continues holding the insert in engagement with the side wall. A more detailed description of this lock pin can be found within the Boyer patent and is incorporated by reference herein. Additional prior art lock pins can be found in Stashko, U.S. Pat. No. 4,632,593, and Stier, U.S. Pat. Nos. 3,484,919 and 3,171,188.
FIG. 2A shows a prior art insert lock 2 presently used by the Applicant. The insert lock 2 includes a shim 4 having a hole for receiving a locking pin 6. The locking pin 6 includes a head portion 7 with a longitudinal axis offset from the longitudinal axis of a body portion 8. This offset forms an eccentric with a throw equal to the distance between the two axes. An insert is seated atop the shim 4 and the entire assembly is mounted in the pocket of a cutting tool. The insert lock 2 operates under the same principles as locking pin taught by Boyer. As in Boyer, if the locking pin 6 is rotated in the proper direction the head portion urges the insert into a secured, cutting position against the side and back walls of the cutting tool's pocket. However, if by mistake, the locking pin 6 is rotated in the opposite direction, then due to the interrelated geometry of the components the insert is forced against the back and side walls and is not in the cutting position even though to the operator it appears to be secured into the cutting position. This mislocation of the insert results in undersized parts and increased wear of the insert.
One proposed solution to this problem has been to place an arrow on the cutting tool indicating the proper direction of rotation for the insert lock 2. However, these arrows fade with time and even under the best of conditions are subject to operator error.
Another problem with the prior art devices is that they can be over rotated in the proper direction forcing the high point of the eccentric past the back wall, which can damage the pin.
Accordingly, a need exists for a insert lock that when rotated in the proper direction would secure the insert into the cutting position, without allowing over rotation, and when rotated in the opposite direction would prevent the insert from being mislocated within the pocket and appearing secured therein.